1. Field of the Invention
The invention relates to a novel protein from the sheep scab mite, Psoroptes ovis, which may be used for eliciting host-protective grooming behavior and/or immune response in cattle.
2. Description of the Prior Art
Psoroptes ovis (Hering) (Acarina: Psoroptidae), the globally distributed sheep scab mite, is an economically important parasite of domestic cattle and sheep, and a serious threat to wild populations of bighorn sheep (Boyce and Brown, 1991, J. Parasitol. 77:675-679). Mite infestation of susceptible cattle can result in the development of scabies lesions. The lesion is consistent with allergic dermatitis (Stromberg and Fisher, 1986, Am. J. Vet. Res., 47:1551-1560) characterized histologically by superficial perivascular dermatitis, marked edema in the superficial dermis, numerous eosinophils, and mast cells (Stromberg and Guillot, 1989, Am. J. Vet. Res., 50: 594-601). The dermatitis can become extensive and lead to the death of cattle in poor condition, and under extremes of environmental stress. It has been suggested that death may occur as a result of the high demand, and consumption of neutrophils at the lesion site, leaving other tissues such as the lungs susceptible to secondary bacterial infection (Stromberg and Guillot, 1987, Vet. Pathol., 24: 365-370).
Stanchioned cattle repeatedly infested with P. ovis appear to develop some level of resistance, defined by a slower rate of lesion and mite population growth (Stromberg and Fisher, 1986, ibid). Guillot and Stromberg (1987, Vet. Parasitol., 10:73-78) suggested that the slow progression of lesion and mite population expansion on stanchioned resistant cattle could be attributed to a lowered ovipositional rate of the female mites, by some unexplained mechanism. Losson et al. (1988, Res. Vet. Sci., 44:197-201) reexposed unstanchioned cattle to P. ovis and the cattle exhibited signs of immediate hypersensitivity including pruritus, scratching, and exudation. Scabies lesions developed on these cattle but healed rapidly and none of the cows developed clinical scabies.
Unfortunately, knowledge of the immunogenicity and allergenicity of purified P. ovis proteins in cattle is limited. In an effort to qualitatively describe mite proteins to which cattle respond, Boyce and Brown (1991, ibid) electrophoretically resolved Psoroptes spp. crude soluble proteins from cattle collected mites. These separated proteins were immunoblotted with serum from a moderately P. spp. infested cow. They found that less than 20 antigens were recognized by antibody in this serum, with bands at 10 and 116 kDa being most prominent. Mathes et al. (1996, Int. J. Parasitol., 26:437-444), working with immune serum from P. ovis infested sheep and crude P. ovis proteins, detected approximately 24 antigenic proteins with dominant bands at 15, 44, 130, and 170 kDa.
Behavioral self-grooming has been shown in other cattle/ectoparasite systems to account for a significant reduction in the ectoparasite numbers (Koudstaal et al., 1978, Parasitol., 76:379-386). Fisher and Wright [1981, Southwestern Entomolog., 6(1):57-61], Guillot (1981, J. Econ. Entomol., 74:653-657) and Losson et al. (1988, ibid) suggested that the stimulation of self-grooming in cattle was significant in natural acquired resistance to P. ovis infestation.
We have discovered a novel antigenic protein which is effective for stimulating antibody production, resulting at least in part in an immediate-type hypersensitivity reaction, in cattle against the sheep scab mite, Psoroptes ovis. In cattle, administration of the protein provides protection from infestation by P. ovis by eliciting a grooming response and/or immunizing the animal against P. ovis. The protein is also effective for producing and/or binding antibodies to P. ovis, and may be used as an immunodiagnostic reagent. The invention also includes isolated DNA sequences encoding the protein, expression vectors containing these sequences, microorganisms or other host cells transformed with these vectors, and recombinant methods for producing the protein.
In accordance with this discovery, it is an object of this invention to provide a protein which is effective for protecting cattle against infestation with P. ovis. 
It is also an object of this invention to provide a protein which is effective for either or both of eliciting an immediate-type hypersensitivity reaction and thus cause a grooming response in cattle against P. ovis, or immunizing the cattle against this pest.
Another object of this invention is to provide a protein effective for producing antibodies which selectively bind to P. ovis for use in assays for this pest.
Yet another object of this invention is to provide a protein which will bind to antibodies made in a host to P. ovis and may be used as an immunodiagnostic reagent.
Still another object of this invention is to provide the genes which encode the protein, which may be used to provide recombinant DNA molecules containing the genes for insertion into host cells and expression of the protein therefrom.
Other objects and advantages of this invention will become readily apparent from the ensuing description.